chemistry eoy9

• The law of conservation of mass states that the total mass of the reactants must equal the total mass of the products in a chemical reaction.
• solid- strongly bonded particles, particles vibrate weakly
• Plum pudding model (jj thompson)- atoms could not be solid spheres (must contain negatively charged electrons )

  General ball of positive charge.
• Nuclear model (Ernest rutherford)

  No space between atoms

  Positive charge is in one specific area (nucleus)

  Electrons orbit nucleus

  experiment-most alpha particles directed at thin sheets of gold passed through showing that all the mass of the atom was deflected in the nucleus, few were deflected or bounced back suggesting positive charge was concentrated at centre of atom
• alpha particle scattering experiment - Rutherford discovered nuclei are positively charged and very small compared to atom size
• Compounds- chemical reactions needed to separate bonds

  chemical bonds between elements

  fixed composition

  mixture— no fixed composition

  no chemical bonds

  Different elements and components can be separated more easily
• Isotopes are atoms of the same element that have different numbers of neutrons
• An atom becomes an ion when its third or last shell is full
• saturated solution- a solution that cannot hold anymore dissolved liquid
• Carbonate CO₃²⁻
• sulphate SO4-2
• hydroxide OH⁻
• nitrate NO₃⁻
• ammonium NH 4 +
• Rf value= distance travelled by substance / distance travelled by solvent
• inks separate because each ink has a different solubility in the solvent and they are all attracted to the stationary phase differently
• Bohr model- electrons orbit nucleus at specific distances, electrons on energy levels or shelves
• oxygen- glowing splint held in test tube- splint relights
• hydrogen- lighted splint held in a test tube- pop sound heard and splint burns rapidly
• carbon dioxide- gas bubbled through limewater, lime water turns milky or cloudy white
• chlorine- damp litmus paper held in a test tube- paper turns white
• temperature does not rise when solid is melting because heat is absorbed to break bonds between solid particles.
• electrolysis (electrical decomposition) is a method of splitting compounds that are more reactive than carbon by passing an electric current through the molten compound
• metal carbonate + acid -> salt + carbon dioxide + water
• an exothermic reaction is one that transfers energy to the surrounding so the temperature surroundings increase (combustion, oxidation and neutralisation)
• an endothermic reaction is one that takes in energy from its surroundings (thermal decomposition)
• potassium -please

  sodium -stop

  lithium -laughing

  calling -calcium

  me -magnesium

  a -aluminium

  (careless) -(carbon)

  zebra -zinc

  instead -iron

  try -tin

  lead- learning

  (how) -hydrogen

  copper - copper

  saves -silver

  gold -gold

  please -platinum
• methane- CH4
• Ethane C2H6
• Propane C3H8
• Butane C4H10
• crude oil is a finite resource found in rocks. it is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• alkanes- most of the hydrocarbons in crude oil are hydrocarbons called alkanes. alkanes only contain single covalent bonds and are classed as saturated hydrocarbons
• crude oil is a mixture of a very large number of compounds. most of the compounds are hydrocarbons which are molecules made of hydrogen and carbon atoms only
• physical properties of hydrocarbons

  some properties of hydrocarbons depend on the size of their molecules. these properties influence how hydrocarbons are used as fuels

  boiling points and viscosity of hydrocarbons increase as the molecules get bigger (because the intermolecular forces become larger as the molecules become bigger)

  volatility (how easily a liquid vaporises)

  flammability of the fuels decrease as the molecules get bigger
• fractional distillation of crude oil

  Oil is preheated then passed into column (some of the oil evaporates)

  Vapours rise up and cool (some vapours condense, separate and flow out the column in a pipe)

  some vapours stay as gases and rise out to the top of the column

  Each fraction has a different boiling point and condenses at different levels in the fractioning column

  Temperature of the column decreases upwards

  Boiling point depends on size of molecules

  Small molecules condense at lower temperatures

  Big molecules condense at higher temperatures
• cracking

  larger hydrocarbons can be broken down to produce smaller, more useful molecules
• alkenes are hydrocarbons with a double carbon-carbon bond. alkenes are more reactive than alkanes
• alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion